Bug#802093: library not linked against libdl

[djcj]

Package: x265
Version: 1.8-2

The shared library is using symbols from libdl but it's not linked 
against it:
$ readelf -s libx265.so.68 | grep dlopen
    32: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT  UND dlopen
$ readelf -d libx265.so.68 | grep libdl
$
I only checked the amd64 version. This should be fixed by appending 
'-ldl' to '-DEXTRA_LIB' in debian/rules.